RTS is one of the hardest genres to identify its origin; some people point to a German Genesis game called... ok I forget what it's called. Personally I would say:

The First: Dune II (as far as point-and-click RTS goes, with the trinity of base building, resource gathering, and combat control)
The Formula: Command & Conquer
The Definer: Starcraft

C&C has a big place in my heart, but even I have to admit people associate the genre with Starcraft.

Unfortunately you all took the genres I could think of... what about Turn Based JRPG's?

The First: Dragon Quest
The Formula: Final Fantasy
The Definer: FFVII (going with my define definition from RTS)